This invention relates to a novel process for preparing a vinylsiloxane-benzocyclobutene, the polymers of which are useful for the preparation of multichip modules and integrated circuits.
Schrock (U.S. Pat. No. 4,812,588) describes a preparation of DVS-bisBCB (divinyltetramethyldisiloxane-bisbenzocyclobutene) involving the reaction between 4-BrBCB (3-bromobicyclo[4.2.0]octa-1,3,5-triene) and DVS-(1,3-divinyl-1,1,3,3-tetramethyldisiloxane) in the presence of a palladium catalyst. ##STR1##
Schrock reported the product of this reaction to be represented by the following structure: ##STR2##
After Schrock's discovery, DeVries et al. (see 12th North American Catalyst Society Meeting, May 5-9, 1991, incorporated herein by reference) reported that the product of the reaction of 4-BrBCB and DVS under the Schrock conditions was, in fact, a mixture of isomers, predominantly the trans,trans isomer, with the trans,gem isomer being the most significant minor product: ##STR3##
One disadvantage of the Schrock method is that the DVS is of limited availability. A second disadvantage is that about 15 to 25% of the products of this reaction are side products. One of these side products, trans-ethylenebisbenzocyclobutene (trans-3,3'-(1,2-ethenediyl)bis[bicyclo(4.2.0)octa-1,3,5-triene]), is formed at percent levels (see U.S. Pat. Nos. 5,243,068 and 5,136,069, incorporated herein by reference) and may sporadically crystallize out of the product mixture, thereby causing both inconsistent product and problematic processing.
Still another disadvantage of the Schrock method is that the products of the method may require treatment with peroxides and extensive purification to remove unacceptably high quantities of phosphorous, bromine, and palladium. (See DeVries et al., U.S. Pat. No. 5,138,081, incorporated herein by reference.)
In view of the deficiencies of the art, it is desirable to find a synthetic route that can produce higher yields of desired vinylsiloxane-BCB products, that uses more readily available materials, and that requires less workup.